Watt-level continuous-wave and high-repetition-rate mid-infrared lasers based on a Er3+-doped Ca0.8Sr0.2F2 crystal

Abstract

A 3 at% Er3+:Ca0.8Sr0.2F2 mixed crystal was grown successfully with a Ca:Sr molar ratio of about 4:1. This was applied as a laser gain medium and pumped by diode laser, obtaining a continuous-wave output power of 1.41 W with a slope efficiency of 39.2%, thus exceeding the Stokes limit by about 5%. Furthermore, with Mn+1XnTx (MXene) as a saturable absorber, passive Q-switched mode-locking operation was experimentally demonstrated for the first time, to the best of our knowledge. Mode-locked pulses under the Q-switched pulse envelope had a high repetition rate of 103.2 MHz at a center wavelength of 2,796.7 nm.